In this tutorial, you will learn to write a distributed ONOS application. The application you will be writing is called BYON (Build Your Own Network). This tutorial will teach you how to implement an ONOS service, an ONOS store, and how to use parts of the CLI and Northbound API.

(Here are some slides that can be used to accompany the tutorial:Slides)

Introduction

Pre-requisites

You will need a computer with at least 2GB of RAM and at least 5GB of free hard disk space. A faster processor or solid-state drive will speed up the virtual machine boot time, and a larger screen will help to manage multiple terminal windows.

The computer can run Windows, Mac OS X, or Linux – all work fine with VirtualBox, the only software requirement.

To install VirtualBox, you will need administrative access to the machine.

The tutorial instructions require prior knowledge of SDN in general, and OpenFlow and Mininet in particular. So please first complete the OpenFlow tutorial and the Mininet walkthrough. Also being familiar with Apache Karaf would be helpful although not entirely required.

Stuck? Found a bug? Questions?

Email us if you’re stuck, think you’ve found a bug, or just want to send some feedback. Please have a look at the guidelines to learn how to efficiently submit a bug report.

Set up your environment

Install required software

You will need to acquire two files: a VirtualBox installer and the latest Tutorial VM from the Downloads page.

After you have downloaded VirtualBox, install it, then go to the next section to verify that the VM is working on your system.

Create Virtual Machine

Double-click on the downloaded tutorial zipfile. This will give you an OVF file. Open the OVF file, this will open virtual box with an import dialog. Make sure you provision your VM with 4GB of RAM and if possible 4 CPUs, if not 2 CPUs should be ok.

Click on import. When the import is finished start the VM and you will be automatically logged in to a running desktop session as show below:

Important Command Prompt Notes

In this tutorial, commands are shown along with a command prompt to indicate the subsystem for which they are intended.

For example,

onos>

indicates that you are in the ONOS command line, whereas

mininet>

indicates that you are in mininet.

Connecting to your tutorial cell

Obtain the IP address of the tutorial cell on from your instructor and setup a PPTP VPN connection using onos as a user and onos as password. The method to this will vary depending on the operating system of the developer machine. The example below shows the setup on OS/X:

Then connect to the ONOS Cluster VPN.

Verifying that ONOS is deployed

Now let's quickly run some tests to make sure everything is ok. Let's start by openning a new terminal window and connecting to the ONOS cli by typing onos

The number of switches per ONOS instance may be different for you because mastership is simply obtained by the first controller which handshakes with the switch. If you would like to rebalance the switch-onos ratio simply run:

onos> balance-masters

And now the output of the masters command should give you something similar to this:

At this point, you multi-instance ONOS deployment is functional. Let's move on to writing some code.

Writing 'Build Your Own Network'

We are now going to start building BYON. BYON is a service which allows you to spawn virtual networks in which each host is connected to every other host of that virtual network. Basically, each virtual network contains a full mesh of the hosts that make it up.

Lab 1: Importing and building an application

We have downloaded some starter code in the ~/onos-byon directory. It contains a root pom.xml file for the project, as well as a initial implementation of the CLI bundle. We can start by importing the entire project into IntelliJ.

First start IntelliJ by double clicking on the IntelliJ icon on your desktop. When you get prompted with the following window.

Select "Import Project" and import the onos-byon project.

Import the project from external model, and select "Maven".

And now make sure you check "Sources" and "Documentation" in the Automatically download section:

And click 'Next' and click next as well on the following window. Now, make sure you pick Java 8 in the next window by first clicking on the green '+' sign and selecting 'java-8-openjdk-amd64' and click 'ok' followed by 'Next'.

Finally click on 'Finish'. You should see the byon source tree on the left sidebar.

The onos-app command will take the oar file that is generated during the build and push it into the specified ONOS instance. The command can also activate the application if you replace install with install! as well as separately activate, deactivate, and uninstall the application. Every time you update your code you simply need to run onos-app $OC1 reinstall! target/byon-1.0-SNAPSHOT.oar and the new application will be loaded and started in the remote ONOS instances.

Let's check that everything works by heading into ONOS and running a couple commands:

The star next to the application indicates that it has been activated. We can try running the list-networks command to display the one fake network that is hard coded in the starter code.

onos> list-networks
my-network

Congratulations! You have successfully built, installed and activated the byon application.

Lab 2: Connect the Manager to the Store

In this part, we are going to implement some of the NetworkManager's methods using the provided store. The store will be used to store the service's network state; however, the implementation that is provided is not distributed. We will build a better store in a later part.

The NetworkManager is going to have to use the store (that we are going to build) to store information therefore we are going to need a reference on a NetworkStore:

Lab 3: Add intents to allow traffic to flow in the virtual networks

In order to be able to use many of ONOS' services, the caller must supply an Application ID. An application ID allows ONOS to identify who is consuming which resources as well as track applications. To achieve this, we ask the CoreService for an application ID in the activate method. You should use the appId when constructing the intents for this part.

We will also need to get a reference to the IntentService. The reference will automatically be injected when the application is loaded after you uncomment the two lines near the top of the NetworkManager.

When addHost() is called, we will need to create an intent between the host and all other hosts that already exist in the network.

You should only to add the intents if this is the first time that the host is added, so be sure to check the store's return value. true indicates that the add was successful i.e. this is the first time.

For this exercise, we will be using HostToHostIntents and you can build one like this:

Lab 4: Implementing removal of hosts from a virtual network

When a host is removed from a network or a network is removed entirely, we need to remove the intent related to that host or network from the IntentService. There are Lab 4 TODOs in the removeHost() and removeNetwork()methods. The starter code also contains a removeIntents() method that you will need to complete. In this method, you will need to get the intents from the IntentService, filter the relevant ones to remove, and then instruct the IntentService to withdrawn them. Note: For your convenience, we have provided a helper method, matches(), that can be used to filter the relevant intents.

Next, we will need to construct some CLI commands so that you can test your work, specifically, one command to remove hosts and another to remove networks.

Start by creating two files in the byon-cli package 'RemoveHostCommand.java'. This CLI command is simple and very similar to the add host CLI command, so do this now as an exercise. When you have written this command, you will need to add the following XML to the 'shell-config.xml' under resources.

Once again if you recompile your code and use onos-app update your application on the ONOS instances. You should now be able to add and remove networks as well as hosts. Try it out!

Now, you should have a fairly complete implementation of the BYON app, but it will only work from one instance. (Try running list-networks on another instance! It will not show you any networks.)

Lab 5: Upgrading the store to make it distributed

The starter implementation of the DistributedNetworkStore uses a ConcurrentMap to store information about the virtual networks. This map only stores the data locally, and it knows nothing about other instances in the cluster. We will be replacing the map with a ConsistentMap which is cluster-aware, and one of the distributed primitives provided by ONOS.

Before we can instantiate a ConsistentMap, we need to get a reference to the StorageService; you can do this by uncommented in the StorageService reference near the top of the DistributedNetworkStore class.

Now that you the networks field is a normal java map that is backed by a distributed map you do not have to change any code at all. And actually you can ignore all the lab 5 todos.

Next, let's recompile your application and push it to the ONOS cluster. You should now be able to create, update, and delete networks from any node, and your distributed store will the application running on all instances in sync. Open a few terminals and test this on the different instances.

Lab 6: Network Events

Components in ONOS can use events to asynchronously notify other components when their state has changed. We will demonstrate how this can be done by creating a new event type, NetworkEvent, to notify listeners when a virtual network has been updated. These events will be fired by the distributed store and forwarded by the manager to listeners in the peer ONOS instance.

With ONOS being a clustered system, it needs to allow managers to learn about events that may have occurred on other cluster nodes. For this reason, in every ONOS subsystem the events are generated within the distributed stores and then are passed to the respective manager components via StoreDelegate interface. Upon receiving the event via the delegate interface, the manager can then take local action and then disseminate the event to its event listeners.

To enable the store/manager delegate relationship, we need to make the existing store interface extend the abstract Store interface as shown below. It basically states that the NetworkStore is capable of having a NetworkStoreDelegate to which it will send NetworkEvent notifications:

And since we changed the interface of the Store we will have to make sure that the implementation, namely DistributedNetworkStore, properly adheres the revised contract. The AbstractStore base class provides methods for setting delegate and for posting events to that delegate.

This listener will need to be added and removed to the networks map during activation and deactivation respectively.

Alright, so now that the stores emit events the managers should be made to receive them. For this we are going to have to add a reference on the EventDeliveryService an ListenerRegistry to keep track of listeners and NetworkStoreDelegate as shown in the code snippet below.

To test this, you will need to create a new component that registers to the NetworkEvents with the NetworkService. We will leave this as an extra credit exercise.

Make sure to use the @Component annotation to start an instance of the class automatically.You will also want to register and deregister with the NetworkService in the activate and deactivate methods of your component.

Finally, build and push the app to the ONOS cluster. You should try to test your implementation. When you add and remove networks and/or hosts you should see this being reflected on the other ONOS instances.

Furthermore, you add, remove, or update a network you should see the following line in the ONOS log. You can get the ONOS log by running: